Thermocouple&RTD Knowledge

What to do if the thermocouple fails?

What to do if the thermocouple fails?Thermocouples have the following common faults:From AnHui TianKang sort out.

Failure phenomenon:

a The thermoelectric potential is smaller than the actual value.

Cause Analysis:

(1) Short circuit.

(2) Short circuit between terminals in the thermocouple junction box.

(3) The compensation wire is short-circuited due to burnt insulation.

(4) The compensation wire does not match the thermocouple.

(5) The polarity of the compensation wire and the thermocouple are reversed.

(6) Insufficient insertion depth and incorrect installation position.

(7) The temperature of the cold junction of the thermocouple is too high.


(1) After inspection, if it is caused by moisture, it can be dried; if it is due to poor insulation of the ceramic tube, it should be replaced.

(2) Open the terminal box and brush the terminal board clean.

(3) Reinsulate the short circuit or replace the compensation wire with a new one.

(4) Replace it with a compensating lead of the same type.

(5) Reconnect correctly.

(6) Change the installation position and insertion depth.

(7) Replace the connecting wire of the thermocouple with a compensation wire to move the cold end away from the high temperature area.

2. The thermoelectric potential is larger than actual.

Cause Analysis:

(1) The compensation lead does not match the thermocouple model.

(2) The insertion depth is insufficient or the installation position is incorrect.

(3) Deterioration of the hot electrode.

(4) An interference signal enters.

(5) The temperature of the reference end of the thermocouple is too high.


(1) Replace the compensation lead of the same type.

(2) Change the installation position or insertion depth.

(3) Replace the thermocouple.

(4) Check the interference source and eliminate it.

(5) Adjust or correct the reference temperature.

3. The measuring instrument indication is unstable, sometimes there is no, sometimes high and low.

Cause Analysis:

(1) The thermal electrode has poor contact at the terminal.

(2) The thermocouple has intermittent short circuit or intermittent grounding.

(3) The thermal electrode has been broken or seems to be broken.

(4) The thermocouple is not securely installed and swings.

(5) The compensation wire has a ground or intermittent short circuit.


(1) Reconnect.

(2) Take out the hot electrode of the thermocouple from the protective tube, find out the fault point and eliminate it.

(3) Replace with a new electrode.

(4) The installation is firm.

(5) Find the fault point and eliminate it.

4. Large thermocouple potential error.

Cause Analysis:

(1) Deterioration of the hot electrode.

(2) The installation position and installation method of the thermocouple are improper.

(3) The surface area of the thermocouple protection tube is excessively fouled.

(4) Measure the short circuit (thermocouple and compensation wire).

(5) The thermocouple circuit is disconnected.

(6) The terminal is loose.


(1) Replace the thermocouple.

(2) Change the installation position and installation method.

(3) Clean up.

(4) Replace the insulation at the short circuit.

(5) Find the disconnection and reconnect.

(6) Tighten the terminal.


Contact: Mr Li

Phone: +86-18226665885

Tel: +86-0550-7788337


Add: No.20# RenHe South Road,TianChang,AnHui Province,China

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